Two types of fracture, early and late, have been
reported following limb lengthening in patients with achondroplasia (ACH)
and hypochondroplasia (HCH). We reviewed 25 patients with these conditions who underwent 72
segmental limb lengthening procedures involving the femur and/or
tibia, between 2003 and 2011. Gender, age at surgery, lengthened
segment, body mass index, the shape of the callus, the amount and
percentage of lengthening and the healing index were evaluated to determine
predictive factors for the occurrence of early (within three weeks
after removal of the fixation pins) and late fracture (>
three weeks
after removal of the pins). The Mann‑Whitney U test and Pearson’s
chi-squared test for univariate analysis and stepwise regression
model for multivariate analysis were used to identify the predictive factor
for each fracture. Only one patient (two tibiae) was excluded from
the analysis due to excessively slow formation of the regenerate,
which required supplementary measures. A total of 24 patients with
70 limbs were included in the study. There were 11 early fractures in eight patients. The shape of
the callus (lateral or central callus) was the only statistical
variable related to the occurrence of early fracture in univariate
and multivariate analyses. Late fracture was observed in six limbs
and the mean time between removal of the fixation pins and fracture
was 18.3 weeks (3.3 to 38.4). Lengthening of the tibia, larger healing
index, and lateral or central callus were related to the occurrence
of a late fracture in univariate analysis. A multivariate analysis
demonstrated that the shape of the callus was the strongest predictor
for late fracture (odds ratio: 19.3, 95% confidence interval: 2.91
to 128). Lateral or central callus had a significantly larger risk
of fracture than fusiform, cylindrical, or concave callus. Radiological monitoring of the shape of the callus during distraction
is important to prevent early and late fracture of lengthened limbs
in patients with ACH or HCH. In patients with thin callus formation,
some measures to stimulate bone formation should be considered as
early as possible. Cite this article:
Our aim was to determine whether abnormalities noted on MRI immediately after reduction for developmental dysplasia of the hip could predict the persistance of dysplasia and aid surgical planning. Scans of 13 hips in which acetabular dysplasia had resolved by the age of four years were compared with those of five which had required pelvic osteotomy for persisting dysplasia. The scans were analysed by two consultant musculoskeletal radiologists who were blinded to the outcome in each child. The postreduction scans highlighted a number of anatomical abnormalities secondary to developmental dysplasia of the hip, but statistical analysis showed that none were predictive of persisting acetabular dysplasia in the older child, suggesting that the factors which determine the long-term outcome were not visible on these images.
